• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.541-546
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• 2005

Tracking control of an automatic pipe cutting robot (APCROMB) is studied. Using magnetic force APCROMB, which is designed and developed in Kyung Hee University, binds itself to the pipe and executes unmanned cutting process. The gravity effect on the movement of APCROMB varies as it rotates around the cylindrical pipe laid in the gravitational field. To maintain a constant velocity and consistent cutting performance against the varying gravitational effect, the authors adopt a multi-rate repetitive learning controller (MRLC), which learns the required effort to cancel the repetitive tracking errors caused by nonlinear effect. In addition to the varying gravity effect other types of nonlinear disturbances including backlash in the driving system and the slip between the wheels of APCROMB and the pipe also cause degradation in the cutting process. In order to identify those nonlinear disturbances the position estimation based on the encoder attached at the motor is not good enough. To identify the absolute angular position of APCROMB the authors propose the angular position estimation based on the signals from a MEMS-type two-axis accelerometer mounted on APCROMB. The tracking performances of APCROMB with a MRLC using the encoder-based position estimation is experimentally measured and results are shown. Also the difference between the encoder-based angular displacement measurement and the accelerometerbased angular displacement measurement is included.

• Computers and Concrete
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• 제15권6호
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• pp.879-902
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• 2015

The remaining service life (RSL) of buildings has been an important issue in the field of building and facility management, and its development is also one of the essential factors for achieving sustainable infrastructure. Since the estimation of RSL of buildings is heavily affected by the subjectivity of individual inspector or engineer, much effort has been placed in the development of a rational method that can estimate the RSL of existing buildings more quantitatively using objective measurement indices. Various uncertain factors contribute to the deterioration of the structural performance of buildings, and most of the common building structures are constructed not with a single structural member but with various types of structural components (e.g., beams, slabs, and columns) in multistory floors. Most existing RSL estimation methods, however, consider only an individual factor. In this study, an estimation method for RSL of concrete buildings is presented by utilizing a fuzzy theory to consider the effects of multiple influencing factors on the deterioration of durability (e.g., concrete carbonation, chloride attack, sulfate attack), as well as the current structural condition (or damage level) of buildings.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.717-721
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• 2010

Soil volume conversion factors are used for estimation of an excavated the soil volume which will be removed or added in levelling the ground surface of a construction site. An accurate evaluation method will help us reduce a construction cost and time consuming. In this study, we performed the laboratory tests, including grain size measurement, water content, specific gravity, porosity, density and XRD tests, to suggest reliable soil volume conversion factors and weathering indices in field using nondestructive methods. The weathering index and soil volume conversion factor L are obtained for different types of soils. At results, the CIW index is the best method measuring the weathering index and the factor L is relative to natural porosity, void ratio, density and dry density.

• 조명전기설비학회논문지
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• 제26권2호
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• pp.51-60
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• 2012

An improved method for detecting fault distance in overhead transmission lines is described in this paper. Based on single-ended measurement, propagation theory of traveling waves together with the wavelet transform technique is used. In estimating fault location, a simple, but fundamental method using the time difference between the two consecutive peaks of transient signals is considered; however, a new method to enhance measurement sensitivity and its accuracy is sought. The algorithm is developed based on the lattice diagram for traveling waves. Representing both the ground mode and alpha mode of traveling waves, in a lattice diagram, several relationships to enhance recognition rate or estimation accuracy for fault location can be found. For various cases with fault types, fault locations, and fault inception angles, fault resistances are examined using the proposed algorithm on a typical transmission line configuration. As a result, it is shown that the proposed system can be used effectively to detect fault distance.

• 소음진동
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• 제9권6호
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• pp.1131-1136
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• 1999

NIC@E is the software developed by authors. The program provides the noise level in outdoors due to various noise source types : construction machines including blast sources, railroad vehicles and automobiles. It operates in the Windows system. In this paper, a highway traffic noise has been evaluated using various types of approach : Ray-tracing method, NIRI method, JAS method. In order to compare the noise estimation performance for various models, a measurement is conducted on a 8 lane express highway at the distance of 25 m and 50 m from the lane. The result shows that the ray tracing and JAS model predict the measured value well within 2dB deviaton. The NIRI model, however, underestimates the highway noise level, as the distance between the source and receiver increases.

• 로봇학회논문지
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• 제17권3호
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• pp.296-302
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• 2022

This paper proposes a center of plantar foot pressure (CoP) trajectory estimation method based on Gaussian process regression, with the aim to show robust results regardless of the regions and numbers of FSRs of the insole sensor. This method can bring an interpolation between the measurement points inside the wearable insole sensor, and two experiments are conducted for performance evaluation. For this purpose, the input data used in the experiment are generated in three types (13 FSRs, 8 FSRs, 5 FSRs) according to the regions and numbers of FSRs. First, the estimation results of the CoP trajectory are compared using Gaussian process regression and weighted mean. As a result of each method, the estimation results of the two methods were similar in the case of 13 FSRs data. On the other hand, in the case of the 8 and 5 FSRs data, the weighted mean varies depending on the regions and numbers of FSRs, but the estimation results of Gaussian process regression showed similar results in spite of reducing the regions and numbers. Second, the estimation results of the CoP trajectory based on Gaussian process regression during several gait cycles are analyzed. In five gait cycles, the previous cycle and the current estimation results are compared, and it was confirmed that similar trajectories appeared in all. In this way, the method of estimating the CoP trajectory based on Gaussian process regression showed robust results, and stability was confirmed by yielding similar results in several gait cycles.

• 한국철도학회논문집
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• 제19권6호
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• pp.755-764
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• 2016

이 논문에서는, 변위-변형률 관계로부터 변위를 추정하는 선행 연구의 현장 적용성을 검토하기 위하여 실교량에 대한 현장재하실험을 실시하고, 그 결과에 대해 고찰하였다. 3경간 연속 IPC 거더 도로교 및 강합성 박스거더 경량전철 교량에 변위계 및 변형률 게이지를 부착하고, 재하차량에 의한 응답을 측정하였다. 현장재하실험을 통해 얻어진 실측 변형률을 변위로 변환시키기 위해 변위와 변형률의 관계를 이용하였다. 해석적인 방법으로 변위-변형률 관계를 도출하기 위해 연구대상 교량을 격자구조로 모형화하고 구조해석을 수행하였다. 연구결과, 사전 구조해석에 의해 얻어진 변위-변형률 관계와 실측 변형률을 이용하여 변위를 추정하여도 실용상 만족할 만한 결과를 도출할 수 있었다. 이 연구 결과는 향후 계측이 어려운 환경하에 놓여 있는 교량의 변위 측정에 널리 활용될 수 있을 것으로 기대된다.

• 전자공학회논문지S
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• 제35S권7호
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• pp.72-85
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• 1998

In this paper, we propose a new method that sequentially estimates TDOA(Time Delay Of Arrival) and FDOA(Frequency Delay Of Arrival) for extracting the information about the bearing and relative velocity of a target in passive radar or sonar arrays. The objective is to efficiently estimate the TDOA and FDOA between two sensor signal measurements, corrupted by correlated Gaussian noise sources in an unknown way. The proposed method utilizes the one dimensional slice function of the third order cumulants between the two sensor measurements, by which the effect of correlated Gaussian measurement noises can be significantly suppressed for the estimation of TDOA. Because the proposed sequential algoritjhm uses the one dimensional complex ambiguity function based on the TDOA estimate from the first step, the amount of computations needed for accurate estimationof FDOA can be dramatically reduced, especially for the cases where high frequency resolution is required. It is demonstrated that the proposed algorithm outperforms existing TDOA/FDOA estimation algorithms based on the ML(maximum likelihood) criterionandthe complex ambiguity function of the third order cumulant as well, in the MSE(mean squared error) sense and computational burden. Various numerical resutls on the detection probability, MSE and the floatingpoint computational burden are presented via Monte-Carlo simulations for different types of noises, different lengths of data, and different signal-to-noise ratios.

• Spatial Information Research
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• 제22권3호
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• pp.47-58
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• 2014

삼림전용 축소를 통한 온실가스 흡수량의 검증 및 인증(MRV: Measurement, Reporting, Verification)이 REDD의 기회비용 산정과정에서 핵심요건으로 부각되고 있다. 본 연구의 목적은 북한 금강산을 사례지역으로 UN-REDD 기회비용 산정과정에서 위성영상을 활용한 MRV의 잠재력을 파악하고, MRV과정에서 발생할 수 있는 입증책임에 관련된 쟁점들을 사전에 점검하는 데 있다. UN-REDD 기회비용을 산정하는 과정에서, MRV에 필요한 지표를 도출하고 위성영상을 활용하여 역사적 벌채율, 토지이용, 토지피복, 탄소저장량 등에 대한 정보의 수집여부를 평가하였다. 위성영상의 육안판독은 금강산의 MRV 여건(산림면적, 산림의 황폐화 추세 등)을 대, 중, 소 3단계의 분류체계에 의거하여 가시적인 기록으로 제시하였다. 위성영상이 국제사법재판소, UN, UN-REDD 등에서 증거자료로 인정되기 때문에 기회비용 산정과정에서 법적으로 구속력을 가진 증빙자료로 활용될 수 있을 것으로 판단된다. 현지조사와 문헌조사를 활용한 MRV에 대해서도 측정자료 확보에 대한 불확실성과 불안으로 인하여 북한의 REDD에 대한 활발한 투자가 어렵게 되고, 북한의 산림보전에 관련된 정부 기업 개인들과 거래하는 것을 꺼려할 정도로 대안이 없는 것이 아니라는 것이 확인되었다. 본 연구를 통해 도출된 결과는 북한에서 REDD사업을 하려는 남측 기업과 GCF(녹색기후기금, Green Climate Fund)를 비롯한 탄소무역 분야에서 실무를 수행하는 관계자들에게 구체적인 참고자료로 활용될 수 있을 것으로 판단된다.

• 한국측량학회지
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• 제40권4호
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• pp.325-332
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• 2022

우주 측지 기술 사이의 상대적인 위치 관계를 설명하는 벡터를 결정하기 위해서는 VLBI IVP (Very Long Baseline Interferometry Invariant Point)의 위치를 정밀하게 계산하여야 한다. 이를 위해 일반적으로 VLBI 안테나에 반사 타겟을 부착한 후 필라들로부터 경사 거리, 수평각, 수직각을 관측한다. 그 다음 단계에서는 관측값과 미지수를 연결하는 수학 모델을 이용하여 조정 계산을 수행하게 된다. 따라서 계산된 미지수는 관측값의 정밀도에 영향을 받게 된다. 이때 특히 문제가 되는 것은 반사 타켓이 일반적인 측량 정밀도를 확보하기 어려운 곳에 위치하고 있다는 점이다. 즉, 반사 타겟의 방향을 조정하여 측량 기기에 정확하게 맞출 수 없다는 것이다. 따라서 이러한 부분은 관측 오차에 또 다른 형태로 나타날 것이며 조정 계산 시 오차 모델링에 오류를 발생시킬 수도 있다. 본 연구에서는 조정 계산 후 계산된 잔차의 특성에 대한 분석을 수행하였다. 먼저 관측 타입별 통계 분석을 통해 정규성을 검정하였으며 분산에 차이가 있는 지에 대한 검정도 실시하였다. 관측 타입별로 등분산 검정을 한 경우 분산이 서로 다른 것으로 나타났다. 각 필라에 대해 관측 타입별 등분산 검정을 했을 때 경사 거리와 수평 및 수직각 사이에는 분산에 차이가 있는 것으로 나타났다. 따라서 결합 측량으로부터 최적의 결과를 얻기 위해서는 관측 오차에 대해 보다 세분화된 모델링이 필요한 것으로 나타났다.